Reversible refrigeration system



Oct. 31, 1961 s. L. MCMILLAN 3,006,164

REVERSIBLE REFRIGERATION SYSTEM Filed Sept. 29, 1960 INVENTOR. STEPHENL. MMILLAN HIS ATTORNEY The present invention relates to an improvedreversible refrigeration system employing a capillary restricting meansbetween the heat exchangers thereof and incorporating an arrangement forcooling the hermetic motor of the system and for changing the flowrestriction in the system when the system is reversed from heating tocooling and vice versa.

An injection cooling arrangement of the above-described type isdisclosed in the invention of the application of James L. Schulze,Serial No. 860,848, filed December 21, 1959, now Patent No. 2,967,410,dated January 10, 1961, and assigned to the assignee of the presentapplication. My present invention is an improvement over the Schulzeinvention which invention was made by the said James L. Schulze prior tomy invention. I, therefore, do not herein claim as my invention anythingshown or described in said Schulze application, which is to be regardedas prior art with respect to this present application.

It is an object of the present invention to provide an improvedarrangement in a reversible refrigeration system for injecting condensedrefrigerant into the hermetic casing for cooling the motor duringoperation of the system in either direction and for automaticallyreducing the flow restriction in the system during the cooling cycle ascompared to that during the heating cycle.

Further objects and advantages of the invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize the invention will be pointed out with particularity in theclaims annexed to and formin a part of this specification.

In accordance with the present invention, there is provided a reversiblerefrigeration system for an air conditioning unit adapted for heatingand cooling an enclosure including a motor-compressor unit sealed withina hermetic casing and connected in reversible refrigerant flowrelationship with an indoor heat exchanger and an outdoor heatexchanger. A first capillary is connected between the heat exchangersfor expanding refrigerant from condenser pressure to evaporator pressureas refrigerant flows through the system. A discharge passage leads fromthe compressor into the hermetic casing for conducting high pressuredischarge gas from the compressor into. the casing for cooling the motorof the unit. A portion of this discharge passage takes the form of anaspirating means, such as a venturi or jet pump, which means creates aregion of lower pressure in the high pressure gas flowing through thepassage. A liquid refrigerant bypass tube is conected in parallel withthe capillary between the heat exchangers so that one of its oppositeends always communicates with condensed refrigerant in one oi the heatexchangers regardless of the direction of refrigerant flow through thesystem. Connecting at some intermediate point on the bypass tube is aliqtL'd refrigerant supply conduit, having its opposite end conmeetingwith the low pressure region of the aspirating means for introducingliquid refrigerant into the aspirating means to be mixed with and tocool the high pressure gas flowing therethrough. On opposite sides ofthe connecting point between the refrigerant bypass tube and therefrigerant conduit leading to the aspirating means are check valves,each operable to permit flow of liquid refrigerant through the tube inthe direction of the refrigerant conduit leading to the aspirating meansbut Bfihdlh i Patented Oct. 31, 39G! preventing flow in the directionaway from the refrigerant conduit. Also connected between the indoorheat exchanger and a point between the check valves of the refrigerantbypass tube is a second capillary adapted to promote flow of refrigerantaround the check valve adjacent the indoor heat exchanger whenrefrigerant flow is in the direction from the outdoor heat exchangertoward the indoor heat exchanger. When the direction of refrigerant flowthrough the system is from the indoor heat exchanger toward the outdoorheat exchanger, the check valve adjacent the outdoor heat exchangercompletely stops flow of refrigerant toward the outdoor heat exchangerexcept through the first capillary connected between the two heatexchangers.

For a better understanding of the invention reference may be had to theaccompanying drawing, thesingle figure of which illustrates in somewhatschematic form a reversible refrigeration system incorporating thepresent invention.

Referring now to the drawing, there is shown a revers ible cycle ofrefrigeration system for use in an air conditioner of the type adaptedto both heat and cool air from an enclosure. 'Fo-r compressing andpumping refrigerant through the system there is provided amotorcompressor unit, generally designated by the reference numeral 2.The motor-compressor unit 2 is mounted in a hermetically sealed casing 3which houses the compressor 4 and its drive motor 6 and which issuitable for containing the high pressure refrigerant gas. A suctionline '7 connects directly with the suction inlet of the compressor andcarries low pressure refrigerant gas to the compressor. A discharge line8 is connected to the case for carrying the high pressure gas fromwithin the .case into the remaining portion of the system. The dischargeand suction lines are both connected to a reversing valve 9. Alsoconnected to the reversing valve E are a pair of conduits l1 and 12which lead respectively to the indoor and outdoor heat exchangers orcoils 13 and '14.

included in the system for the purpose of expanding refrigerant fromcondensing pressure to evaporator pres sure is a first capillaryexpansion means or tube 16. This tube operates as an expansion meansduring both the cooling and heating cycles and maintains a predeterminedpressure differential between the evaporator and condenser regardless ofthe direction of refrigerant flow.

In an air conditioning unit of this type, the indoor coil 13 is arrangedfor heating or cooling air from the enclosure, while the outdoor coil 14is arranged for either rejecting heat to or extracting heat from theoutside atmosphere. The reversing valve 9 is selectively reversible todirect discharge gas into either one of the lines 11 and 12 whilereceiving low pressure gas from the other line, thereby making thesystem reversible for either heating or cooling an enclosure. Thus, ifit is desirable to set this system on the heating cycle, compressordischarge gas flowing through the discharge line 8 is connected by meansof a reversing valve 9 to the line 11 which carties the hot dischargegas to the indoor coil 13. This coil then acts as a condenser to give upits heat to the enclosure air. If it is desired to set the system forcooling the enclosure, the suction line 7 is connected tothe indoor coil13 through a line 11, which then acts as an evaporator, while thedischarge gas is carried to the outdoor coil 14 by the line 12.

During operation of the compressor, low pressure refrigerant iswithdrawn from the suction line 7 which connects with the suction port(not shown) of the compressor unit 6. Low pressure refrigerant gas iscompressed within the compressor unit to a relatively high pressure andtemperature and is then discharged by the compressor through a suitabledischarge passage 17 leading into the hermetic casing 3. For purposes ofillustration, the discharge passage 17 is shown as a tube leading out ofthe hermetic casing and then back into the hermetic casing. However,this discharge passage could he a passage, such as that illustrated inthe aforementioned Schulze application, which leads from the dischargeport of the compressor unit through the main frame 18 and, thence,directly into the hermetic casing 6 without leaving the hermetic case.Included within the discharge passage is an aspirating means or venturisec- =tion, generally designated by the reference numeral 21, throughwhich hot discharge gas passes prior to entering the hermetic case. Thepassage 17 discharges the high pressure gas into the case below themotor and, after flowing upwardly over the motor 6, the high pressuregas is conducted out of the casing through the conduit 8 into theremaining portions of the system.

In order to cool the discharge gas flowing through the discharge passagesufficiently to maintain the motor within safe operating temperatures,cool liquid refrigerant from the heat exchanger operating as -acondenser is introduced into the high pressure discharge stream as itflows through the aspirating means. As may be seen in the drawing, theaspirating means contains a nozzle or gas accelerating section 22 and adiffuser or gas decelerating section 23 separated by a pinched or throatportion 24. As the high pressure discharge gas flows through theaspirating means, it drops in prmsure in the nozzle section 22 where itsvelocity is increased. Then, in the diffuser section of the aspiratingmeans, the gas pressure increases to approximately its original pressureas the velocity of the gas decreases. Thus, a pressure drop or region oflow pressure is created in the throat 24 of the aspirating means whichis easily suflicient to overcome the pressure drop encountered in thecase and tubing of one or the other of the heat exchanges. Thatis, thepressure in the throat 24 is normally less than the pressure in thelatter stages of the heat exchanger operating as a condenser therebycausing liquid or condensed refrigerant to he siphoned through a passageconnecting the aspirating means with the heat exchanger operating as acondenser. When liquid refrigerant is introduced into the throat or lowpressure region of the aspirating means, it encounters the hot dischargegas and is vaporized or flashed into the gaseous form. Heat removed fromthe discharge gas, in vaporizing the liquid refrigerant, reduces thetemperature of the discharge gas and the violent reaction created by theflashing of the liquid into vaporized form completely mixes the gases sothat the resultant gas mixture issuing from the passage is at a uniformtemperature and much cooler than the temperature of the original highpressure gas discharged from the compressor.

Liquid refrigerant is supplied from the heat exchanger operating as acondenser through the passage including a refrigerant supply conduit 26which connects with a refrigerant bypass tube 27, which is in turnconnected between the heat exchangers 13 and 14 in parallel with theexpansion means or capillary 16. The liquid refrigerant supply conduit26 connects with the bypass tube 27 at some intermediate point 25between the two heat exchangers. A pair of check valves, designated thefirst or indoor valve 28 and the second or outdoor valve 29, arearranged respectively on opposite sides of the connecting point 25between the refrigerant bypass tube 27 and the condensed refrigerantsupply conduit 26, and prevent the flow of refrigerant through the tube27 in the direction away from the supply line 26. It may be seen,therefore, that during operation of the reversible cycle refrigerationsystem, refrigerant is permitted to flow through the check valveadjacent the heat exchanger operating as a condenser but is preventedfrom flowing through the check valve adjacent the heat exchangeroperating as an evaporator. Thus liquid refrigerant is always suppliedto the tube 27, and thereby to the refrigerant supply conduit 26regardless of the direction of refrigerant flow through the system. Asmay be seen in the drawing, a. second capillary 36 is positioned inparallel with the check valve 28, or in parallel with the check valve 28adjacent the indoor heat exchanger 13. It can be seen from the drawingthat, when the system is operating on the cooling cycle, refrigerantflows through the check valve 29 into the liquid conduit 26 and thenceinto the discharge passage leading to the compressor. Liquid refrigerantalso flows through the capillary 36 around the indoor check valve 28into the indoor heat exchanger 13. Condensed refrigerant flowing throughthe capillary 36 is expanded to evaporator pressure in the same manneras refrigerant flowing through the first capillary 16. That is, when thesystem is operating on the cooling cycle, refrigerant flows through bothof the capillaries 16 and 36. However, when the system is operated onthe heating cycle, and refrigerant flow is in the reverse direction, orfrom the indoor heat exchanger 13 toward the outdoor heat exchanger 14,it can be seen that, although refrigerant may flow through both of thecapillaries 16 and 36, only the flow through the capillary 16 iseffective. Because of the check valve 29 there is no flow of refrigerantcompletely through the refrigerant bypass tube 27, to the outdoor heatexchanger 14 and the capillary 36 is effectively taken out of thesystem. It should be noted that, during the heating cycle when theindoor heat exchanger 13- is operating as a condenser, high prasurerefrigerant is admitted to both ends of the capillary 36 therebyeliminating the effect of this capillary. Thus, greater restriction isinherently introduced into the systern during operation of the system onthe heating cycle than during operation of the system on the coolingcycle, when both the capillaries 16 and 36 are utilized for expandingrefrigerant from condenser pressure to evaporator pressure.

Liquid refrigerant flowing through the conduit 26 is restricted to someextent by a restricting means or third capillary 31. The design of therestricting means or third capillary 31 should be such as to permitenough condensed refrigerant to flow through the conduit 26 to sufficiently cool the discharge gas but still limit the flow sufficientlyto eliminate short circuiting of the evaporator (or the heat exchangeroperating as an evaporator) and eventual collection of refrigerant inliquid form within the case. Obviously, a capillary does not have to beused for this purpose. Other means, such as a needle valve or other typeof restriction could easily be substituted for this capillary.

In operation, the venturi section or aspirating means 21 acts as amodulating device for supplying greater or lesser amounts of condensedrefrigerant to cool the high pres sure discharge gas according to theflow of gas through the discharge passage from the condenser unit. Sincethe amount of liquid refrigerant flowing through the supply conduit 26depends to a great extent upon the pressure recovery experienced in thediffuser section 23 from the throat 24 to the outlet of the diffuserand, since the amount of pressure recovery in the venturi or aspiratingmeans is a function of the quantity of gas flowing therethrough, it isapparent that the amount of liquid refrigerant siphoned through theliquid refrigerant supply conduit 26 depends upon the quantity ofdischarge gas flowing through the discharge passage 17 leading from thecompressor unit. Whenever the pressure of the suction gas is high, thetemperature of the gas at the discharge outlet of the compressor 6 is,under normal conditions, correspondingly greater and the coolingrequirement is, therefore, greater. However, when the suction pressureis high, a correspondingly greater quantity of gas is pumped whichresults in a greater flow of liquid refrigerant through the passage andthrough the throat 24 thereby increasing the flow of liquid refrigerantthrough the conduit 26 and supplying the neces' sary cooling of the hightemperature discharge gas. Con

versely, when the suction pressure is low and the compressed dischargegas is at a relatively low temperature, the amount of gas being pumpedthrough the discharge passage 17 is correspondingly less. This,consequently, produces a correspondingly smaller pressure differencebetween the throat 24 and the outlet of the aspirating means, therebyresulting in a diminished flow through the conduit 26 and a lesseramount of cooling of the discharge gas. Thus, under most conditions ofoperation, the aspirating means automatically modulates the amount ofcooling of the discharge gas from the compressor, and automaticallyincreases or decreases the cooling effect on this gas to maintain themotor within safe operating limits.

By the present invention there has been provided an improved arrangementin a reversible refrigeration system for providing injection cooling ofa compressormotor unit regardless of the direction of refrigerant flowthrough the system which arrangement also serves to automaticallyincrease the flow restriction in the system during operation on theheating cycle and to automatically reduce the flow restriction in thesystem during operation thereof on the cooling cycle.

While in accordance with the patent statutes there has been describedwhat at present is considered to be the preferred embodiment of thepresent invention, it will be obvious to those skilled in the art thatvarious changes and modifications may be made therein without departingfrom the invention, and it is, therefore, the aim of the appended claimsto cover all such changes and modifications as fall within the truespirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A reversible refrigeration system for an air conditioning unitadapted for heating and cooling an enclosure comprising amotor-compressor unit, an indoor heat exchanger and an outdoor heatexchanger connected in reversible refrigerant flow relationship, a firstcapillary connected between said heat exchangers for expandingrefrigerant from condenser pressure to evaporator pressure, means forreversing the flow of refrigerant through said system thereby to operateeach of said heat exchangers interchangeably as a condenser or as anevaporator, said motor-compressor unit being mounted in a hermeticallysealed casing for containing a high pressure refrigerant gas, adischarge passage leading from said compressor into said casing forconducting compressed refrigerant from said compressor into said casingfor cooling said motor, said discharge passage including an aspiratingmeans for creating a low pressure region in said discharge gas stream asit passes through said aspirating means, a refrigerant bypass tubeconnected between said heat exchangers in parallel with said firstcapillary, a liquid refrigerant supply conduit connecting at one endwith said refrigerant bypass tube and at the other end with saidaspirating means for introducing liquid refrigerant into said dischargepassage for cooling said high pressure refrigerant gas flowing throughsaid discharge passage, check valves in said refrigerant bypass tube onopposite sides of the connection with said liquid refrigerant supplyconduit for preventing flow of liquid refrigerant through said tube inthe direction of said heat exchanger being operated as an evaporatorduring either cycle of operation of said system, and a second capillarymeans having one end connected to said refrigerant bypass tube at somepoint between said check valves and having its other end connecting withsaid indoor heat exchanger for introducing expanded refrigerant intosaid indoor heat exchanger during operation of said system on thecooling cycle when said indoor heat exchanger operates as an evaporator.

2. A reversible refrigeration system for an air conditioning unitadapted for heating and cooling an enclosure comprising amotor-compressor unit, an indoor heat exchanger and an outdoor heatexchanger connected in reversible refrigerant flow relationship, a firstcapillary connected between said heat exchangers for expandingrefrigerant from condenser pressure to evaporator pressure, means forreversing the flow of refrigerant through said system thereby to operateeach of said heat exchangers interchangeably as a condenser or as anevaporator, said motor-compressor unit being mounted in a hermeticallysealed casing for containing high pressure refrigerant gas, a dischargepassage leading from said compressor into said casing for conductingcompressed refrigerant from said compressor into said casing for coolingsaid motor, said discharge passage including an aspirating means forcreating a low pressure region in said discharge gas stream as it passesthrough said aspirating means, a refrigerant bypass tube connectedbetween said heat exchangers in parallel with said first capillary, arefrigerant supply conduit connecting at one end with said refrigerantbypass tube and at the other end with said aspirating means forintroducing liquid refrigerant into said discharge passage for coolingsaid high pres sure refrigerant gas flowing through said dischargepassage, a first check valve in said refrigerant bypass tube betweensaid connection with said refrigerant conduit and said indoor heatexchanger, a second check valve in said refrigerant bypass tube betweensaid connection with said refrigerant conduit and said outdoor heatexchanger, said first check valve preventing flow of liquid refrigerantthrough said refrigerant bypass tube in the direction toward said indoorheat exchanger and said second check valve preventing flow of liquidrefrigerant through said refrigerant bypass tube in the direction towardsaid outdoor heat exchanger, and a second capillary means bypassing saidfirst check valve and having one end connected to said refrigerantbypass tube and the other end connecting with said indoor heat exchangerfor introducing expanded refrigerant from said refrigerant bypass tubeinto said indoor heat exchanger during operation of said system on thecooling cycle when said indoor heat exchanger operates as an evaporator.

3. A reversible refrigeration system for an air conditioning unitadapted for heating and cooling an enclosure comprising amotor-compressor unit, an indoor heat exchanger and an outdoor heatexchanger connected in reversible refrigerant flow relationship, a firstcapillary connected between said heat exchangers for expandingrefrigerant from condenser pressure to evaporator pressure, means forreversing the flow of refrigerant through said system thereby to operateeach of said heat exchangers interchangeably as a condenser or as anevaporator, said motor-compressor unit being mounted in a hermeticallysealed casing for containing a high pressure refrigerant gas, adischarge passage leading from said compressor into said casing forconducting compressed refrigerant from said compressor into said casingfor cooling said motor, said discharge passage including an aspiratingmeans for creating a low pressure region in said discharge gas stream asit passes through said aspirating means, a refrigerant bypass tubeconnected between said heat exchangers in parallel with said firstcapillary, a liquid refrigerant supply conduit connecting at one endwith said refrigerant bypass tube and at the other end with saidaspirating means for introducing liquid refrigerant into said dischargepassage for cooling said high pressure refrigerant gas flowing throughsaid discharge passage, check valves in said refrigerant bypass tube onopposite sides of said connection with said liquid refrigerant supplyconduit for preventing flow of liquid refrigerant through said tube inthe direction of said heat exchanger being operated as an evaporatorduring either cycle of operation of said system, a second capillarymeans having one end communicating with said refrigerant bypass tube atsome point between said check valves and having the other end connectingwith said indoor heat exchanger for introducing refrigerant into saidindoor heat exchanger during operation of said system on a cooling cyclewhen said indoor heat exchanger operates as an evaporator, and a thirdcapillary in said liquid refrigerant supply conduit for restricting theflow of liquid refrigerant therethrough toward said aspirating means andpreventing short circuiting of refrigerant around said heat exchangeroperating as an evaporator.

References Cited in the file of this patent UNITED STATES PATENTS CoyneNov. 15, 1960

